HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Server-Sent Events Example</title>
</head>
<body>
  <h1>Real-Time Clock</h1>
  <div id="clock">--:--:--</div>
  <p id="status">Click Start to begin.</p>
  <button type="button" id="start">Start</button>
  <button type="button" id="stop">Stop</button>

  <script>
    var timer = null;

    function showTime(data) {
      document.getElementById('clock').textContent = data;
    }

    document.getElementById('start').onclick = function () {
      if (timer) return;
      document.getElementById('status').textContent = 'Streaming...';
      timer = setInterval(function () {
        showTime(new Date().toLocaleTimeString());
      }, 1000);

      // With a real SSE server:
      // var es = new EventSource('http://localhost:8080');
      // es.onmessage = function (e) { showTime(e.data); };
      // es.onerror = function () {
      //   document.getElementById('status').textContent = 'Connection error. Retrying...';
      // };
    };

    document.getElementById('stop').onclick = function () {
      clearInterval(timer);
      timer = null;
      document.getElementById('status').textContent = 'Stopped.';
    };
  </script>
</body>
</html>

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SSE — Real-Time Clock Demo